CN112090099A - MVR and multi-effect evaporation combined system and solution concentration method adopting MVR and multi-effect evaporation combined system - Google Patents
MVR and multi-effect evaporation combined system and solution concentration method adopting MVR and multi-effect evaporation combined system Download PDFInfo
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- 238000001704 evaporation Methods 0.000 title claims abstract description 86
- 230000008020 evaporation Effects 0.000 title claims abstract description 83
- 238000000034 method Methods 0.000 title claims abstract description 39
- 239000000243 solution Substances 0.000 claims abstract description 83
- 239000011550 stock solution Substances 0.000 claims abstract description 61
- 239000011552 falling film Substances 0.000 claims description 98
- 238000000926 separation method Methods 0.000 claims description 84
- 239000007788 liquid Substances 0.000 claims description 74
- 239000002351 wastewater Substances 0.000 claims description 53
- 239000002253 acid Substances 0.000 claims description 43
- 239000000498 cooling water Substances 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 15
- 239000000203 mixture Substances 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 10
- 239000003513 alkali Substances 0.000 claims description 9
- 238000005406 washing Methods 0.000 claims description 9
- 238000007599 discharging Methods 0.000 claims description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 6
- 239000012141 concentrate Substances 0.000 claims description 5
- 239000003518 caustics Substances 0.000 claims description 4
- 230000006835 compression Effects 0.000 claims description 3
- 238000007906 compression Methods 0.000 claims description 3
- 230000009290 primary effect Effects 0.000 claims 2
- 125000004122 cyclic group Chemical group 0.000 abstract description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 13
- 238000009835 boiling Methods 0.000 description 6
- 238000005265 energy consumption Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 238000009270 solid waste treatment Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/26—Multiple-effect evaporating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/22—Evaporating by bringing a thin layer of the liquid into contact with a heated surface
Abstract
The invention provides an MVR and multi-effect evaporation combined system and a solution concentration method adopting the same, wherein a stock solution is preheated and then enters an MVR system for primary concentration; and (3) the concentrated solution after MVR primary concentration enters a multi-effect evaporation system adopting steam as a heat source, and is further concentrated to the concentration required by the product. The invention combines the characteristics of MVR evaporation concentration process and multi-effect evaporation concentration process, reduces the operation cost of evaporation concentration of the dilute solution with a specific medium, and realizes the cyclic utilization of system resources. The invention combines the characteristics of MVR evaporation concentration process and multi-effect evaporation concentration process, reduces the operation cost of evaporation concentration of the dilute solution with a specific medium, and realizes the cyclic utilization of system resources.
Description
Technical Field
The invention relates to a dilute solution evaporation and concentration production process, in particular to an MVR and multi-effect evaporation combined system and a solution concentration method adopting the MVR and multi-effect evaporation combined system.
Background
In the waste water produced by some chemical plants and metallurgical plants in China, 5-10% dilute sulfuric acid solution exists, and the traditional treatment method adopts Ca (OH) to dilute acid2Neutralization is carried out, and a large amount of solid waste is generated by the method. With the increasing requirement of environmental protection, the solid waste treatment cost generated by the traditional treatment method is higher and higher.
The dilute sulfuric acid is concentrated and recycled by adopting an evaporation concentration method, and the recycling of waste acid is one of the directions for solving the problems. The dilute sulfuric acid evaporation concentration needs a large amount of energy consumption and is poor in economical efficiency. The existing concentration process has two ways, one is MVR (mechanical vapor recompression) technology, and the other is multi-effect evaporation technology.
MVR (mechanical vapor recompression) is actually an open heat pump system, converts electric energy into heat energy through a vapor compressor, and has low system energy consumption and good economical efficiency. However, MVR systems have two disadvantages: a. the one-time investment cost of the system is high; b. due to the limitation of the pressure ratio of the vapor compressor, the operation evaporation temperature is low, and the method is not suitable for the concentration of the solution with higher boiling point.
The multiple-effect evaporation is a traditional evaporation concentration process, and a typical multiple-effect evaporation process is as follows: a plurality of falling-film evaporators are adopted, steam is used as a one-effect heat source, the steam generated by evaporation of the one-effect evaporator is used as a heat source of the next-effect falling-film evaporator, evaporation concentration is carried out in a multi-effect series connection mode in sequence, different heat is utilized in a grading mode, and efficient utilization of system energy is improved. Compared with an MVR system, the system has the advantages that: a. the one-time investment of the equipment is low; b. the method is suitable for the working condition that the boiling point of the solution is greatly changed in the concentration process. The disadvantages are that: the energy consumption is higher, and the running cost is higher.
The characteristics of the evaporation concentration of the dilute sulfuric acid are as follows: the concentration ratio is high, the energy consumption is high, and the boiling point is greatly changed along with the increase of the concentration. By conventional multi-effect evaporation with Ca (OH)2Compared with the neutralization process, the process has poor economy, so that the traditional multi-effect evaporation process is not generally applied.
Disclosure of Invention
The invention aims to solve the problems of high energy consumption and poor economical efficiency of the traditional multiple-effect evaporation, provides an MVR and multiple-effect evaporation combined system and a solution concentration method adopting the MVR and multiple-effect evaporation combined system, solves the economic problem of evaporation concentration of dilute sulfuric acid and certain dilute salt solutions, and has industrial popularization value.
In order to solve the technical problem, an embodiment of the present invention provides a MVR and multi-effect evaporation combined system, which includes a MVR system for first concentrating a stock solution and a multi-effect evaporation system for concentrating a concentrated solution to a concentration required by a product.
The MVR system comprises a vapor compressor, a one-effect falling film evaporator, a one-effect separating tank and an alkaline washing tower, and the multi-effect evaporation system is a two-effect or more-than-two-effect evaporation system.
Further, the MVR system comprises a steam compressor, a first-effect falling-film evaporator, a first-effect separation tank and an alkaline washing tower, the multi-effect evaporation system comprises a first-stage stock solution preheater, a second-stage stock solution preheater, a condensate tank, a second-effect separation tank, a third-effect falling-film evaporator, a third-effect separation tank, a tail gas condenser, a condensate waste water storage tank, an exhaust steam condenser, a waste water storage tank, a stock solution feed pump, a condensate pump, a second-effect feed pump, a third-effect feed pump, a first waste water pump, a second waste water pump, a concentrated solution cooler and a second-effect falling-film evaporator, an inlet of the stock solution feed pump is connected with a dilute solution storage tank, an outlet of the stock solution feed pump is connected with a shell pass inlet of the concentrated solution cooler, a shell pass outlet of the concentrated cooler is connected with a tube pass inlet of the first-stage stock solution preheater, a tube pass outlet of the first-stage stock solution preheater is connected, the tube side outlet of the secondary raw liquid preheater is connected with the tube side inlet of the primary falling-film evaporator, the tube side outlet of the primary falling-film evaporator is connected with the vapor-liquid mixing inlet of the primary separating tank, the vapor outlet of the primary separating tank is connected with the acid-containing vapor inlet of the alkaline tower, and the acid-free vapor outlet of the alkaline tower is connected with the shell side inlet of the primary falling-film evaporator through a vapor compressor;
the shell pass outlet of the first-effect falling-film evaporator is connected with a condensate inlet of a condensate tank, the condensate outlet of the condensate tank is connected with a shell pass inlet of a first-stage raw liquid preheater, and the shell pass outlet of the first-stage raw liquid preheater is connected with a wastewater discharge port;
the dilute acid solution outlet of the first-effect separation tank is connected with the tube side inlet of the three-effect falling-film evaporator through a three-effect feed pump, the tube side outlet of the third-effect falling-film evaporator is connected with the vapor-liquid mixing inlet of the three-effect separation tank, the vapor outlet of the three-effect separation tank is connected with the inlet of a tail gas condenser, the condensate outlet of the tail gas condenser is connected with the inlet of a condensate waste water storage tank, and the outlet of the condensate waste water storage tank is connected with a waste water outlet through a first waste water pump;
a triple-effect concentrated solution outlet of the triple-effect separation tank is connected with a tube pass inlet of the double-effect falling-film evaporator through a double-effect feed pump, a tube pass outlet of the double-effect falling-film evaporator is connected with a vapor-liquid mixing inlet of the double-effect separation tank, a vapor outlet of the double-effect separation tank is connected with a shell pass inlet of the third-stage falling-film evaporator, a shell pass outlet of the third-stage falling-film evaporator is connected with a condensate inlet of an exhaust steam condenser, a condensate outlet of the exhaust steam condenser is connected with an inlet of a waste water storage tank, and an outlet of the waste water storage tank is connected with a waste water outlet through a second water pump;
a high-temperature dilute acid concentrated solution outlet of the double-effect separation tank is connected with a tube pass inlet of a concentrated acid cooler through a double-effect discharge pump, and a tube pass outlet of the concentrated acid cooler is connected with a concentrated solution outlet;
the shell pass inlet of the two-effect falling-film evaporator is connected with the high-temperature steam tank, the shell pass outlet of the two-effect falling-film evaporator is connected with the shell pass inlet of the secondary raw liquid preheater, and the shell pass outlet of the secondary raw liquid preheater is connected with the condensed water outlet.
Wherein, the vapor outlet of the condensate tank is connected with the shell pass inlet of the one-effect falling-film evaporator through a vapor compressor.
Wherein, be connected with cooling water inlet tube and cooling water outlet pipe on the tail gas condenser. And the exhaust steam condenser is connected with a cooling water inlet pipe and a cooling water outlet pipe.
Wherein, the alkali wash tower is connected with an alkali liquor circulating pump.
The invention also provides a solution concentration method adopting the MVR and multi-effect evaporation combined system, which comprises the following steps:
step 1, preheating a dilute solution stock solution: heating the dilute solution to 80-120 ℃ after sequentially passing through a stock solution feed pump, a concentrated solution cooler, a primary stock solution preheater and a secondary stock solution preheater;
Step 2.1, feeding the dilute solution stock solution preheated in the step 1 into a tube pass of a one-effect falling film evaporator to carry out one-effect falling film evaporation concentration;
2.2, the vapor-liquid mixture after the first-effect heating concentration enters a first-effect separation tank for vapor-liquid separation;
2.3, the gas separated by the first-effect separation tank enters an alkaline washing tower, and the gas is circularly sprayed in the tower through an alkaline liquor circulating pump to remove acid in the gas;
2.4, the gas after alkali washing enters a steam compressor for compression and temperature rise;
2.5, the vapor compressed and heated by the vapor compressor enters the shell pass of the one-effect falling-film evaporator to be used as a heat source to heat and concentrate the dilute acid stock solution;
step 2.6, the condensate generated after heat exchange enters a condensate tank, and the condensate is discharged from the bottom of the condensate tank;
step 2.7, enabling the condensate discharged from the condensate tank to enter a primary stock solution preheater through a condensate pump to preheat the dilute acid stock solution, and then discharging the dilute acid stock solution out of the system;
step 3, multiple-effect evaporation concentration system
3.1, enabling the dilute acid solution subjected to the one-effect evaporation and concentration in the one-effect separation tank to enter a three-effect falling film evaporator through a three-effect feed pump;
step 3.2, performing falling film evaporation concentration on the solution in a tube pass of the triple-effect falling film evaporator, and feeding the vapor-liquid mixture subjected to triple-effect heating concentration into a triple-effect separation tank;
3.3, performing vapor-liquid separation on the vapor-liquid mixture from the three-effect falling film evaporator in a three-effect separation tank;
3.4, the gas separated by the triple-effect separation tank enters a tail gas condenser, is cooled by process cooling water, and is discharged out of the system through a first waste water pump after a condensate waste water storage tank is generated after cooling;
3.5, feeding the triple-effect concentrated solution subjected to vapor-liquid separation in the triple-effect separation tank into a double-effect falling film evaporator through a double-effect feed pump;
3.6, performing falling film evaporation concentration on the triple-effect concentrated solution in the tube pass of the double-effect falling film evaporator;
3.7, the vapor-liquid mixture after the double-effect heating concentration enters a double-effect separation tank for vapor-liquid separation;
3.8, introducing the vapor generated by the separation of the two-effect separation tank into the shell pass of the three-effect falling-film evaporator to serve as a heat source of the three-effect falling-film evaporator to heat, evaporate and concentrate the solution;
step 3.9, condensing the heating steam into condensate after heat exchange in the triple-effect falling-film evaporator, enabling the condensate to enter an exhaust steam condenser, cooling the condensate by process cooling water, enabling the condensate to enter a wastewater storage tank, and then discharging the condensate out of the system through a wastewater pump;
and 4, cooling the multi-effect concentrated solution: the high-temperature concentrated solution after vapor-liquid separation in the double-effect separation tank enters the tube pass of the concentrated solution cooler through the double-effect discharge pump, is cooled by the dilute acid stock solution from the stock solution feed pump and then is discharged out of the system to obtain a concentrated acid solution;
step 5, primary liquid secondary preheating: condensate generated after shell pass steam heat exchange of the two-effect falling-film evaporator enters a shell pass of a secondary stock solution preheater to preheat dilute acid stock solution, and steam condensate after heat exchange and cooling returns to a condensate system.
The technical scheme of the invention has the following beneficial effects: in the invention, the stock solution is preheated and then enters an MVR (mechanical vapor recompression) system for the first concentration; concentrated solution after MVR (mechanical vapor recompression) primary concentration enters a multi-effect evaporation system adopting steam as a heat source, and is further concentrated to the concentration required by the product. The invention combines the characteristics of an MVR (mechanical vapor recompression) evaporation concentration process and a multi-effect evaporation concentration process, reduces the operation cost of evaporation concentration of a dilute solution with a specific medium (the boiling point of the solution changes greatly along with the concentration), and realizes the cyclic utilization of system resources.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Description of reference numerals:
1. a vapor compressor; 2. a one-effect falling film evaporator; 3. a first effect separation tank; 4. an alkaline washing tower; 5. a primary stock solution preheater; 6. a secondary stock solution preheater; 7. a condensate tank; 8. a two-effect separation tank; 9. a triple effect falling film evaporator; 10. a three-effect separation tank; 11. a tail gas condenser; 12. a condensate wastewater storage tank; 13. a dead steam condenser; 14. a wastewater storage tank; 15. a stock solution feed pump; 16. a condensate pump; 17. an alkali liquor circulating pump; 18. a two-effect feed pump; 19. a three-effect feed pump; 20. a first waste water pump; 21. a second waste water pump; 22. a concentrated solution cooler; 23. two-effect falling film evaporator.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the present invention provides a MVR and multi-effect evaporation combined system, which comprises an MVR system and a multi-effect evaporation system, wherein the MVR (mechanical vapor recompression) + multi-effect evaporation combined evaporation concentration system is adopted for a dilute acid stock solution. Preheating the stock solution, and then firstly entering an MVR (mechanical vapor recompression) system for primary concentration; concentrated solution after MVR (mechanical vapor recompression) primary concentration enters a multi-effect evaporation system adopting steam as a heat source, and is further concentrated to the concentration required by the product.
The multi-effect evaporation system can adopt two-effect or more than two-effect evaporation systems according to the process requirements, and the multi-effect evaporation system of the embodiment is a two-effect evaporation system.
In the embodiment, the MVR system comprises a steam compressor 1, a one-effect falling-film evaporator 2, a one-effect separation tank 3 and a caustic tower 4, the multi-effect evaporation system comprises a primary raw liquid preheater 5, a secondary raw liquid preheater 6, a condensate tank 7, a two-effect separation tank 8, a three-effect falling-film evaporator 9, a three-effect separation tank 10, a tail gas condenser 11, a condensate waste water storage tank 12, an exhaust steam condenser 13, a waste water storage tank 14, a raw liquid feed pump 15, a condensate pump 16, an alkali liquor circulating pump 17, a two-effect feed pump 18, a three-effect feed pump 19, a first waste water pump 20, a second waste water pump 21, a concentrated liquid cooler 22 and a two-effect falling-film evaporator 23, an inlet of the raw liquid feed pump 15 is connected with a dilute solution storage tank, an outlet of the raw material feed pump 15 is connected with a shell pass inlet of the concentrated liquid cooler 22, a shell pass outlet of the concentrated cooler 22 is connected with a tube pass inlet of the primary raw liquid, the tube pass outlet of the primary raw liquid preheater 5 is connected with the tube pass inlet of the secondary raw liquid preheater 6, the tube pass outlet of the secondary raw liquid preheater 6 is connected with the tube pass inlet of the primary falling-film evaporator 2, the tube pass outlet of the primary falling-film evaporator 2 is connected with the vapor-liquid mixing inlet of the primary separating tank 3, the vapor outlet of the primary separating tank 3 is connected with the acid-containing vapor inlet of the alkaline tower 4, and the acid-free vapor outlet of the alkaline tower 4 is connected with the shell pass inlet of the primary falling-film evaporator 2 through the vapor compressor 1.
The shell pass outlet of the single-effect falling-film evaporator 2 is connected with a condensate inlet of a condensate tank 7, a condensate outlet of the condensate tank 7 is connected with a shell pass inlet of a primary raw liquid preheater 5, and a shell pass outlet of the primary raw liquid preheater 5 is connected with a wastewater discharge port.
The diluted acid solution outlet of the first-effect separation tank 3 is connected with the tube side inlet of the third-effect falling-film evaporator 9 through a third-effect feed pump 19, the tube side outlet of the third-stage falling-film evaporator 9 is connected with the vapor-liquid mixed inlet of the third-effect separation tank 10, the vapor outlet of the third-effect separation tank 10 is connected with the inlet of the tail gas condenser 11, the condensate outlet of the tail gas condenser 11 is connected with the inlet of the condensate waste water storage tank 12, and the outlet of the condensate waste water storage tank 12 is connected with the waste water outlet through a first waste water pump 20.
The three-effect concentrated solution outlet of the three-effect separation tank 10 is connected with the tube pass inlet of the two-effect falling-film evaporator 23 through the two-effect feed pump 18, the tube pass outlet of the two-effect falling-film evaporator 23 is connected with the vapor-liquid mixing inlet of the two-effect separation tank 8, the vapor outlet of the two-effect separation tank 8 is connected with the shell pass inlet of the three-stage falling-film evaporator 9, the shell pass outlet of the three-stage falling-film evaporator 9 is connected with the condensate inlet of the dead steam condenser 13, the condensate outlet of the dead steam condenser 13 is connected with the inlet of the waste water storage tank 14, and the outlet of the waste water storage tank 14 is connected with the waste water outlet through the second water pump 21.
The high-temperature dilute acid concentrated solution outlet of the double-effect separation tank 8 is connected with the tube pass inlet of the concentrated acid cooler 22 through a double-effect discharge pump, and the tube pass outlet of the concentrated acid cooler 22 is connected with a concentrated solution discharge port.
The shell pass inlet of the two-effect falling-film evaporator 23 is connected with the high-temperature steam tank, the shell pass outlet of the two-effect falling-film evaporator 23 is connected with the shell pass inlet of the secondary raw liquid preheater 6, and the shell pass outlet of the secondary raw liquid preheater 6 is connected with the condensed water outlet.
And a vapor outlet of the condensate tank 7 is connected with a shell pass inlet of the one-effect falling-film evaporator 2 through a vapor compressor 1. And the tail gas condenser 11 is connected with a cooling water inlet pipe and a cooling water outlet pipe. And the exhaust steam condenser 13 is connected with a cooling water inlet pipe and a cooling water outlet pipe. The alkali wash tower 4 is connected with an alkali liquor circulating pump 17.
In the invention, the concentrated solution cooler 22 is arranged to exchange heat between the feed stock solution and the multi-effect concentrated product solution through the cooler, so that the product concentrated solution is cooled to the required temperature, and meanwhile, the stock solution to be concentrated is preheated, thereby improving the thermal efficiency of the MVR system. A secondary stock solution preheater is arranged, condensate generated by steam after first-effect heat exchange with the multi-effect evaporation system exchanges heat with feed stock solution from the concentrated acid cooler, the stock solution is further heated to the feed temperature required by the MVR system, and the thermal efficiency of the MVR system can be improved. And a dead steam condenser and a tail gas condenser are arranged, and tail steam from the last effect separation tank and dead steam of the last effect falling film evaporator are condensed and recovered, so that the tail steam emission of the system meets the environmental protection requirement.
The invention also provides a solution concentration method adopting the MVR and multi-effect evaporation combined system, which comprises the following steps:
step 1, preheating a dilute solution stock solution: the dilute solution is heated to 80-120 ℃ after sequentially passing through a stock solution feed pump 15, a concentrated solution cooler 22, a primary stock solution preheater 5 and a secondary stock solution preheater 6, and the requirement of the MVR system on the feed temperature is met;
Step 2.1, feeding the dilute solution stock solution preheated in the step 1 into a tube pass of a one-effect falling film evaporator 2 for one-effect falling film evaporation concentration;
2.2, the vapor-liquid mixture after the first-effect heating concentration enters a first-effect separation tank 7 for vapor-liquid separation;
2.3, the gas separated by the first-effect separation tank 7 enters an alkaline washing tower 4, and is circularly sprayed in the tower through an alkaline liquor circulating pump 17 to remove acid in the gas;
2.4, the gas after alkali washing enters a steam compressor 1 for compression and temperature rise;
2.5, the vapor compressed and heated by the vapor compressor 1 enters the shell pass of the one-effect falling-film evaporator 2 to be used as a heat source to heat and concentrate the dilute acid stock solution;
step 2.6, the condensate generated after heat exchange enters a condensate tank 7, and the condensate is discharged from the bottom of the condensate tank 7;
step 2.7, enabling the condensate discharged from the condensate tank 7 to enter a primary stock solution preheater 5 through a condensate pump 16 to preheat the dilute acid stock solution, and then discharging the dilute acid stock solution out of the system;
step 3, multiple-effect evaporation concentration system
3.1, enabling the diluted acid solution subjected to the one-effect evaporation concentration in the one-effect separation tank 3 to enter a three-effect falling film evaporator 9 through a three-effect feed pump 19;
step 3.2, the solution is subjected to falling film evaporation concentration in the tube pass of the triple-effect falling film evaporator 9, and the vapor-liquid mixture after triple-effect heating concentration enters a triple-effect separation tank 10;
3.3, carrying out vapor-liquid separation on the vapor-liquid mixture from the three-effect falling film evaporator 9 in a three-effect separation tank 10;
3.4, the gas separated by the triple-effect separation tank 10 enters a tail gas condenser 11, is cooled by process cooling water, and is discharged out of the system through a first waste water pump 20 after being cooled to generate a condensate waste water storage tank 12;
3.5, feeding the triple-effect concentrated solution subjected to vapor-liquid separation in the triple-effect separation tank 10 into a double-effect falling film evaporator 7 through a double-effect feed pump 18;
step 3.6, the triple-effect concentrated solution is subjected to falling film evaporation concentration in the tube pass of the double-effect falling film evaporator 7;
3.7, the vapor-liquid mixture after the double-effect heating concentration enters a double-effect separation tank 8 for vapor-liquid separation;
3.8, introducing the vapor generated by the separation of the two-effect separation tank 8 into the shell pass of the three-effect falling-film evaporator 9 to serve as a heat source of the three-effect falling-film evaporator 9 for heating, evaporating and concentrating the solution;
step 3.9, condensing the heating steam after heat exchange in the three-effect falling-film evaporator 9 into condensate, feeding the condensate into an exhaust steam condenser 13, cooling the condensate by process cooling water, feeding the condensate into a waste water storage tank 14, and discharging the condensate out of the system through a waste water pump 21;
and 4, cooling the multi-effect concentrated solution: the high-temperature concentrated solution after vapor-liquid separation in the double-effect separation tank 8 enters the tube pass of the concentrated solution cooler 22 through the double-effect discharge pump, is cooled by the dilute acid stock solution from the stock solution feed pump 15 and then is discharged out of the system to obtain a concentrated acid solution;
step 5, primary liquid secondary preheating: condensate generated after shell pass steam heat exchange of the two-effect falling-film evaporator 23 enters the shell pass of the secondary stock solution preheater 6 to preheat dilute acid stock solution, and steam condensate after heat exchange and cooling returns to a condensate system.
The invention combines the characteristics of MVR (mechanical vapor recompression) process and multi-effect evaporation process, and is suitable for medium industrial concentration occasions with large boiling point rise in the process of concentrating dilute solution in a large concentration ratio than evaporating and concentrating. Compared with the traditional multi-effect evaporation system, the operation cost can be reduced by more than 1/3 in the application of concentrating 5-10% dilute sulfuric acid into 50% concentrated sulfuric acid, and the economic value is very high.
The invention has the following beneficial effects:
1. the invention utilizes the characteristic of high heat efficiency of MVR (mechanical vapor recompression), concentrates the stock solution at a low concentration stage, evaporates most of the solvent, saves energy and reduces the system operation cost.
2. The invention is suitable for the medium with larger boiling point rise in the evaporation concentration process of dilute solution with large concentration ratio, and expands the application range of MVR (mechanical vapor recompression). The problem of resource recycling of specific industrial scenes can be solved.
3. The invention greatly strengthens mass transfer and heat transfer in the mixing process and carries out partial oxidation reaction.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (8)
1. The MVR and multi-effect evaporation combined system is characterized by comprising an MVR system for concentrating stock solution for the first time and a multi-effect evaporation system for concentrating concentrated solution to the concentration required by a product.
2. The MVR and multi-effect evaporation combined system of claim 1, wherein the MVR system comprises a vapor compressor 1, a one-effect falling film evaporator 2, a one-effect knockout drum 3, and a caustic scrubber 4, and the multi-effect evaporation system is a two-effect or more than two-effect evaporation system.
3. The MVR and multi-effect evaporation combined system according to claim 1 or 2, wherein the MVR system comprises a vapor compressor 1, a one-effect falling film evaporator 2, a one-effect separation tank 3, and a caustic tower 4, the multi-effect evaporation system comprises a primary raw liquid preheater 5, a secondary raw liquid preheater 6, a condensate tank 7, a secondary separation tank 8, a three-effect falling film evaporator 9, a three-effect separation tank 10, a tail gas condenser 11, a condensate waste water storage tank 12, a steam exhaust condenser 13, a waste water storage tank 14, a raw liquid feed pump 15, a condensate pump 16, a secondary feed pump 18, a three-effect feed pump 19, a first waste water pump 20, a second waste water pump 21, a concentrated liquid cooler 22, and a secondary falling film evaporator 23, an inlet of the raw liquid feed pump 15 is connected with a dilute solution storage tank, an outlet of the raw liquid feed pump 15 is connected with a shell pass inlet of the concentrated liquid cooler 22, a shell pass outlet of the concentrated liquid cooler 22 is connected with a tube pass inlet of the primary raw liquid preheater 5, the tube pass outlet of the primary raw liquid preheater 5 is connected with the tube pass inlet of the secondary raw liquid preheater 6, the tube pass outlet of the secondary raw liquid preheater 6 is connected with the tube pass inlet of the primary falling-film evaporator 2, the tube pass outlet of the primary falling-film evaporator 2 is connected with the vapor-liquid mixing inlet of the primary effect separation tank 3, the vapor outlet of the primary effect separation tank 3 is connected with the acid-containing vapor inlet of the alkaline tower 4, and the acid-free vapor outlet of the alkaline tower 4 is connected with the shell pass inlet of the primary falling-film evaporator 2 through the vapor compressor 1;
a shell pass outlet of the first-effect falling-film evaporator 2 is connected with a condensate inlet of a condensate tank 7, a condensate outlet of the condensate tank 7 is connected with a shell pass inlet of a primary raw liquid preheater 5, and a shell pass outlet of the primary raw liquid preheater 5 is connected with a wastewater discharge port;
the dilute acid solution outlet of the first-effect separation tank 3 is connected with the tube side inlet of a three-effect falling-film evaporator 9 through a three-effect feed pump 19, the tube side outlet of the third-effect falling-film evaporator 9 is connected with the vapor-liquid mixing inlet of the three-effect separation tank 10, the vapor outlet of the three-effect separation tank 10 is connected with the inlet of a tail gas condenser 11, the condensate outlet of the tail gas condenser 11 is connected with the inlet of a condensate waste water storage tank 12, and the outlet of the condensate waste water storage tank 12 is connected with a waste water outlet through a first waste water pump 20;
a triple-effect concentrated solution outlet of the triple-effect separation tank 10 is connected with a tube pass inlet of a double-effect falling-film evaporator 23 through a double-effect feed pump 18, a tube pass outlet of the double-effect falling-film evaporator 23 is connected with a vapor-liquid mixing inlet of a double-effect separation tank 8, a vapor outlet of the double-effect separation tank 8 is connected with a shell pass inlet of a three-stage falling-film evaporator 9, a shell pass outlet of the three-stage falling-film evaporator 9 is connected with a condensate inlet of an exhaust steam condenser 13, a condensate outlet of the exhaust steam condenser 13 is connected with an inlet of a waste water storage tank 14, and an outlet of the waste water storage tank 14 is connected with a waste water outlet through a second water pump 21;
a high-temperature dilute acid concentrated solution outlet of the double-effect separation tank 8 is connected with a tube pass inlet of a concentrated acid cooler 22 through a double-effect discharge pump, and a tube pass outlet of the concentrated acid cooler 22 is connected with a concentrated solution outlet;
the shell pass inlet of the two-effect falling-film evaporator 23 is connected with the high-temperature steam tank, the shell pass outlet of the two-effect falling-film evaporator 23 is connected with the shell pass inlet of the secondary raw liquid preheater 6, and the shell pass outlet of the secondary raw liquid preheater 6 is connected with the condensed water outlet.
4. The MVR and multi-effect evaporation combined system according to claim 3, characterized in that the vapor outlet of the condensate tank 7 is connected to the shell-side inlet of the one-effect falling-film evaporator 2 via a vapor compressor 1.
5. The MVR and multi-effect evaporation combined system of claim 3, wherein the tail gas condenser 11 is connected with a cooling water inlet pipe and a cooling water outlet pipe.
6. The MVR and multi-effect evaporation combined system according to claim 3, wherein a cooling water inlet pipe and a cooling water outlet pipe are connected to the exhaust steam condenser 13.
7. The MVR and multi-effect evaporation combined system according to claim 3, wherein a lye circulating pump 17 is connected to the caustic tower 4.
8. A method of solution concentration using the MVR and multi-effect evaporation combined system of any of claims 1-7, comprising the steps of:
step 1, preheating a dilute solution stock solution: the dilute solution is heated to 80-120 ℃ after sequentially passing through a stock solution feed pump 15, a concentrated solution cooler 22, a primary stock solution preheater 5 and a secondary stock solution preheater 6;
step 2, concentrating the MVR system
Step 2.1, feeding the dilute solution stock solution preheated in the step 1 into a tube pass of a one-effect falling film evaporator 2 for one-effect falling film evaporation concentration;
2.2, the vapor-liquid mixture after the first-effect heating concentration enters a first-effect separation tank 7 for vapor-liquid separation;
2.3, the gas separated by the first-effect separation tank 7 enters an alkaline washing tower 4, and is circularly sprayed in the tower through an alkaline liquor circulating pump 17 to remove acid in the gas;
2.4, the gas after alkali washing enters a steam compressor 1 for compression and temperature rise;
2.5, the vapor compressed and heated by the vapor compressor 1 enters the shell pass of the one-effect falling-film evaporator 2 to be used as a heat source to heat and concentrate the dilute acid stock solution;
step 2.6, the condensate generated after heat exchange enters a condensate tank 7, and the condensate is discharged from the bottom of the condensate tank 7;
step 2.7, enabling the condensate discharged from the condensate tank 7 to enter a primary stock solution preheater 5 through a condensate pump 16 to preheat the dilute acid stock solution, and then discharging the dilute acid stock solution out of the system;
step 3, multiple-effect evaporation concentration system
3.1, enabling the diluted acid solution subjected to the one-effect evaporation concentration in the one-effect separation tank 3 to enter a three-effect falling film evaporator 9 through a three-effect feed pump 19;
step 3.2, the solution is subjected to falling film evaporation concentration in the tube pass of the triple-effect falling film evaporator 9, and the vapor-liquid mixture after triple-effect heating concentration enters a triple-effect separation tank 10;
3.3, carrying out vapor-liquid separation on the vapor-liquid mixture from the three-effect falling film evaporator 9 in a three-effect separation tank 10;
3.4, the gas separated by the triple-effect separation tank 10 enters a tail gas condenser 11, is cooled by process cooling water, and is discharged out of the system through a first waste water pump 20 after being cooled to generate a condensate waste water storage tank 12;
3.5, feeding the triple-effect concentrated solution subjected to vapor-liquid separation in the triple-effect separation tank 10 into a double-effect falling film evaporator 7 through a double-effect feed pump 18;
step 3.6, the triple-effect concentrated solution is subjected to falling film evaporation concentration in the tube pass of the double-effect falling film evaporator 7;
3.7, the vapor-liquid mixture after the double-effect heating concentration enters a double-effect separation tank 8 for vapor-liquid separation;
3.8, introducing the vapor generated by the separation of the two-effect separation tank 8 into the shell pass of the three-effect falling-film evaporator 9 to serve as a heat source of the three-effect falling-film evaporator 9 for heating, evaporating and concentrating the solution;
step 3.9, condensing the heating steam after heat exchange in the three-effect falling-film evaporator 9 into condensate, feeding the condensate into an exhaust steam condenser 13, cooling the condensate by process cooling water, feeding the condensate into a waste water storage tank 14, and discharging the condensate out of the system through a waste water pump 21;
and 4, cooling the multi-effect concentrated solution: the high-temperature concentrated solution after vapor-liquid separation in the double-effect separation tank 8 enters the tube pass of the concentrated solution cooler 22 through the double-effect discharge pump, is cooled by the dilute acid stock solution from the stock solution feed pump 15 and then is discharged out of the system to obtain a concentrated acid solution;
step 5, primary liquid secondary preheating: condensate generated after shell pass steam heat exchange of the two-effect falling-film evaporator 23 enters the shell pass of the secondary stock solution preheater 6 to preheat dilute acid stock solution, and steam condensate after heat exchange and cooling returns to a condensate system.
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